Conventional computing devices enable a user to input a choice or a selection in different ways. For example, a user can use an alphanumeric keyboard, a cursor control device or a microphone to indicate a choice or selection. Moreover, touch sensing technology can be used to provide an input selection to a computing device or other types of electronic devices.
Within the broad category of touch sensing technology there exist capacitive sensing touch sensors, commonly referred to as capacitive touchpads or simply touchpads. Touchpads are typically implemented with a flat or planar input (sensing) region or surface; that is, the surface that a user places his or her finger on is typically flat. Other types of capacitive touchpads utilize non-planar sensing surfaces, shaped as a concave or convex bowl, for example. Capacitance sensor elements are distributed underneath the sensing surface and are separated from the sensing surface by intervening material. When the user's finger is placed on the sensing surface, a capacitance is induced in the sensor elements.
Non-planar touchpads can be problematic if the capacitance sensor elements are planar, because the thickness of material between the sensing surface and the sensor elements will be non-uniform. Hence, a capacitive coupling between an object (e.g., a user's finger) and the sensor elements will be non-uniform. If the capacitance sensor elements are made to conform to the shape of the sensing surface, the touchpad may be more costly to manufacture.